Filter apparatus

ABSTRACT

A disk-type filter comprising a housing having an inlet connectable to an upstream pipe and an outlet connectable to a downstream pipe, and a stack of filter units disposed within said housing for separating solid particles from a fluid flowing between filter units in said stack of filter units from an upstream side of said stack of filter units to a downstream side thereof, characterized in that said stack of filter units includes a plurality of co-operating filter units defining a plurality of paired co-operating filter surfaces, including first and second surfaces each defining a plurality of fingers, said fingers defined by said first surface being arranged in registration with said fingers defined by said second surface, the exteriors of said fingers defined by said first and second surfaces communicating with either one of an upstream side and a downstream side and the interiors of said fingers defined by said first and second surfaces communicating with the other one of said upstream side or downstream side, spaces being defined in association with said fingers defined by said first and second surfaces and being disposed in registration so as to define channels, which permit particulate matter to become disengaged with said upstream side of said fingers defined by said first and second surfaces.

This is a continuation of 07/838,540, filed on Feb. 19, 1992, (now U.S.Pat. No. 5,213,684), which is a continuation of 07/150,246, filed Jan.29, 1988, (now U.S. Pat. No. 5,098,565).

FIELD OF THE INVENTION

The present invention relates to filter apparatus and systems generallyand to techniques for operating such apparatus and systems.

BACKGROUND OF THE INVENTION

Various types of filters are known for filtering water and similarliquids. A particularly useful type of filter is a disk filter. Filtersof this type are described and claimed, for example, in applicant's U.S.patent applications Ser. Nos. 647,094, filed Sep. 4, 1984, which is nowU.S. Pat. No. 4,624,785; 709,371, filed Mar. 7, 1985, which is nowabandoned; 709,372, filed Mar. 7, 1985, which is now U.S. Pat. No.4,683,060; 709,373, filed Mar. 7, 1985, which is now U.S. Pat. No.4,654,143; and U.S. Pat. Nos. 4,026,806; 4,042,504; 4,045,345;4,271,018; 4,278,540; 4,295,963.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved filter for use infiltering fluids, such as water.

There is thus provided in accordance with a preferred embodiment of thepresent invention, a disk-type filter comprising a housing having aninlet connectable to an upstream pipe and an outlet connectable to adownstream pipe and a stack of filter units disposed within the housingfor separating solid particles from a fluid flowing between filter unitsin the stack of filter units from an upstream side of the stack offilter units to a downstream side thereof, characterized in that thestack of filter units includes a plurality of co-operating filter unitsdefining a plurality of paired co-operating filter surfaces, includingfirst and second surfaces each defining a plurality of fingers, thefingers defined by the first surface being arranged in registration withthe fingers defined by the second surface, the exteriors of the fingersdefined by the first and second surfaces communicating with either oneof an upstream side and a downstream side and the interiors of thefingers defined by the first and second surfaces communicating with theother one of the upstream side or downstream side, spaces being definedin association with the fingers defined by the first and second surfacesand being disposed in registration so as to define channels, whichpermit particulate matter to become disengaged with the upstream side ofthe fingers defined by the first and second surfaces.

According to a further preferred embodiment of the present invention,there is provided a filter unit comprising first and second surfacesdefining a plurality of fingers, spaces being defined in associationwith the fingers defined by the first and second surfaces such that whena plurality of filter units are disposed in registration, the spacesdefine channels.

Further in accordance with a preferred embodiment of the presentinvention, the fingers defined by the first and second surfaces eachhave formed thereon a pair of spaced, generally raised line portionsseparated by an interior area, the raised line portions on at least oneof the first and second surfaces defining a plurality of spaced grooves.

Still further in accordance with a preferred embodiment of the presentinvention, the filter also comprises a filter aid operatively associatedwith the stack of filter units.

Additionally in accordance with a preferred embodiment of the presentinvention, the pluralities of spaced grooves defined by the first andsecond surfaces define an enhanced depth filtering pathway.

Still further in accordance with a preferred embodiment of the presentinvention, there is provided a planar divider at the interior area ofeach of the fingers, such that when a plurality of filter units aredisposed in registration, the line portions and the planar dividersdefine a multiplicity of backflow chambers for enhanced backflowing.

Further in accordance with a preferred embodiment of the presentinvention, the stack of filter units comprises a generally cylindricalelement having an axial central bore along its longitudinal axis.

Still further in accordance with a preferred embodiment of the presentinvention, there is provided apparatus for providing a flushing fluidflow through the filter unit including a fluid discharge device arrangedfor axial movement along the bore.

Additionally in accordance with a preferred embodiment of the presentinvention, flushing chambers are defined between the line portions.

Further in accordance with a preferred embodiment of the presentinvention, there is provided a plurality of axial connecting elementswhich traverse the stack of filter units at locations intermediate innerand outer diameters of the stack of filter units.

Still further in accordance with a preferred embodiment of the presentinvention, there is provided a manifold defining the inlet and theoutlet in communication with the bottom of the housing.

According to a further preferred embodiment of the present invention,there is provided a filter comprising a housing having an aperture atthe bottom thereof, a filtering assembly disposed in the housing, and amanifold defining an inlet and an outlet in communication with theaperture.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a partially cut-away side view sectional illustration of afilter constructed and operative in accordance with a preferredembodiment of the present invention;

FIG. 2 is a sectional illustration taken along the lines II--II of FIG.1;

FIG. 3 is a sectional illustration corresponding to that of FIG. 2 butillustrating a dual nozzle variety of filter otherwise similar to thesingle-nozzle variety shown in FIGS. 1 and 2;

FIG. 4 is a pictorial illustration of the curved configuration of one ofthe stack of filter elements shown in FIG. 1;

FIG. 5 is a pictorial illustration of a portion of a stack of filterelements of the type shown in FIG. 4;

FIG. 6 is an enlarged illustration of a portion of the stack of filterelements illustrated in FIG. 5;

FIG. 7 is an enlarged illustration of a portion of the stack of filterelements illustrated in FIG. 5, also showing filter cake and/or sedimentassociated therewith;

FIG. 8 is an illustration of part of the stack of filter elementsillustrated in FIG. 5, illustrating the channels between finger elementsthereof;

FIGS. 9A and 9B correspond to FIG. 8 and illustrate the part of thestack of filter elements with filter aid material in associatedtherewith and with the filter aid material having fallen therefromrespectively;

FIG. 10 is a partially cut-away side view sectional illustration of afilter constructed and operative in accordance with a preferredembodiment of the present invention and arranged to define a drainoutlet which is spaced from the bottom of the upstream side of thehousing;

FIG. 11 is a partially cut-way side view sectional illustration of afilter constructed and operative in accordance with another preferredembodiment of the present invention, arranged to define a drain outletwhich is spaced from the bottom of the upstream side of the housing andto include filter stack supports which traverse the filter disksintermediate the upstream and downstream surfaces of the filter disks;

FIG. 12 is a planar view illustration of a filter disk constructed andoperative in accordance with a preferred embodiment of the invention foruse in the apparatus of FIG. 11;

FIGS. 13A and 13B are first and second illustrations showing, inexaggerated form, the bendability of the fingers defined by the filterdisk of FIG. 12 under respective filtration and backflowing conditions;

FIG. 14 is a pictorial illustration of a portion of a filter stackincluding filter disks of the type illustrated in FIG. 2, andillustrating, in exaggerated form, the disengagement of filter aidmaterial from the filter stack as the fingers snap back upon terminationof the application of a pressure gradient thereacross;

FIGS. 15A and 15B are enlarged sectional views of a portion of thefilter stack of FIG. 14 respectively during filtration and duringregeneration or backflowing;

FIG. 16 is a partially cut-way side view sectional illustration of afilter constructed and operative in accordance with yet anotherpreferred embodiment of the present invention, arranged to define acentral drain outlet and fluid inlet manifold and to include filterstack supports which traverse the filter disks intermediate the upstreamand downstream surfaces of the filter disks;

FIG. 17 is an enlarged illustration of the central drain outlet andfluid inlet manifold of FIG. 16;

FIG. 18 is a sectional illustration taken along the lines XVIII--XVIIIof FIG. 17; and

FIG. 19 is a sectional illustration of an alternative embodiment ofcentral drain outlet and fluid inlet manifold constructed and operativein accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made to FIGS. 1, 2 and 3 which illustrate a filterconstructed and operative in accordance with a preferred embodiment ofthe present invention and comprising a base 70 on which is fixedlysupported a bottom housing portion 72. Removably mounted onto the bottomhousing portion 72 is a top housing portion 74, which is maintained insealing engagement therewith by means of a sealing ring 76.

A fluid inlet 78 is provided adjacent the bottom of housing portion 72and communicates with the outside cylindrical surface, hereinaftertermed the "upstream surface", of a stack of filter elements 79. A fluidoutlet assembly 80 is coupled to housing portion 72 and communicationswith a hollow interior portion 81 of stack of filter elements 79adjacent the inner cylindrical surface of the stack of filter elements,hereinafter termed the "downstream surface".

The stack of filter elements 79 preferably comprises a stack of hollowcenter filter disks 82 of the type illustrated in FIGS. 4-9B and 12-15B.

The stack of filter elements 79 is preferably removably mounted incoaxial relationship so as define volume 81 and is retained in suitablytight engagement by means of top and bottom retaining collars 84 and 86joined by a plurality of threaded rods 88, typically four in number, andassociated nuts 90. A retaining member 89 supports top retaining collar84 and is sealingly mounted onto the top housing portion 74 by athreaded retaining ring 91. A collar member 92 engages retaining member89. As seen in FIG. 2, each of the filter elements 82 is preferablyformed with four locating protrusions 85, each formed to permitengagement with a rod 88. Thus it may be appreciated that rods 88 serveto maintain the filter elements 82 in precise azimuthal registration.

A focussed jet nozzle assembly 100 is disposed mainly within volume 81and comprises a water supply shaft 110 having a water inlet 112 and anassociated inlet valve 114.

A rotatable focussed jet outlet head 116 is arranged for relatively freerotation about a rotation axis 118 defined in shaft 110 and is providedwith a single output aperture 119. Referring now to FIG. 2, it is seenthat the outlet aperture is arranged to provide an eccentric wateroutlet jet which drives the outlet aperture 119 in rotary motion aboutaxis 118, thus sequentially directing the output jet into each of theazimuthally separated backflow chambers 121 defined by the adjacentfilter disks 82.

According to a preferred embodiment of the invention, there is providedabove outlet aperture 119 a positioning ring 120, curved to correspondto the curvature of the inner, downstream, surface 122 of the stack offilter elements, for desired positioning of the focussed jet nozzleassembly 100 in volume 81, whereby the axis of rotation of the focussedjet outlet head 116 is centered with respect to cylindrical downstreamsurface 122, such that the output aperture 119 is always at apredetermined distance from the downstream surface 122, so as not tointerfere with the rotation of focussed jet outlet head 116.

It may be appreciated that the focussed water jet exiting from outletaperture 119 is forced into the individual volumes defined by the stackof filter elements facing the outlet aperture, providing efficientflushing of the accumulated solid material collected therein, and is notpermitted to be spread out, which would result in a reduction of itsstrength and its backflowing efficiency.

The outlet aperture 119 is displaced up and down and rotated about axis118, and the pressurized stream produced thereby is sequentiallyconcentrated on individual filtering chambers 121 defined in the stackof filter elements to provide enhanced backflowing thereof.

As noted above, outlet aperture 119 is arranged to provide a radiallydirected concentrated backflowing jet, which serves to flush particulatematter from the stack of filter elements 79.

Inlet 112 is typically coupled via a flexible hose (not shown) to abackflow liquid supply which may be connected to a pressurized source ofliquid to be filtered 123 which communicates with the inlet 78 via a twoway valve 125. Alternatively the inlet 112 may be coupled to anothersource of high pressure fluid. Valve 125 selectably couples the waterinlet 78 of the filter either to a pressurized water source or to abackflow liquid drain 127.

During normal operation of the filter of the present invention, focussedjet nozzle assembly 100 is located partly within volume 81 and shaft 110is sealingly coupled to the top portion 74 of the housing by means ofsealing collar 92 which sealingly engages threading on retaining member89. Valve 125 is oriented as shown in FIG. 1 such that liquid to befiltered enters from the pressurized source and passes to inlet 78 andthrough the stack of filter elements 79 from the upstream surface to thedownstream surface, being filtered to the process. The filtered liquidpasses through volume 81. Valve 114 is closed.

During backflow operation, valve 125 is manipulated to close off thepressurized liquid source and to provide communication between inlet 78and backflow drain 127. Valve 114 is opened to provide a pressurizedflow of water to focussed jet nozzle assembly 100 and collar 92 isdisconnected.

Focussed jet outlet head 116 is manually reciprocated axially along theinterior of the stack of filter elements at the downstream surface andis rotated by the fluid stream eccentrically exiting therefrom throughat least 360 degrees, causing a high pressure concentrated jet of waterto enter the backflow chambers 121 from the downstream surface of thefilter for dislodging accumulated filtered material from the upstreamside of the stack of filter elements. This arrangement enablessubstantially all of the backflow chambers 121 to be thus scanned,region by region, by the concentrated jet for efficient backflowcleaning of the stack of filter elements.

Reference is now made to FIG. 3, which illustrates an alternativeembodiment of the apparatus of FIG. 1, wherein a focussed jet outlethead 132 having two nearly but not exactly oppositely directed eccentricoutlet apertures 134 and 136 is provided. According to a preferredembodiment, the two apertures 134 and 136 are arranged at differentaxial locations with respect to axis 118, thus providing nearlysimultaneous flushing of chambers at two different axial locations alongaxis 118.

Reference is now made to FIGS. 4-9B, which illustrate a preferredembodiment of filter element constructed and operative in accordancewith a preferred embodiment of the invention. The filter element isappropriate for use in any suitable filter apparatus, and isparticularly useful in the filter apparatus described hereinabove.

FIG. 4 illustrates in plan view a portion of a filter disk 420comprising a plurality of finger elements 422. It is seen that theconfiguration of the finger element 422 is preferably not exactlyradial. Specifically, the outline of each finger element is curved alonga portion of an arc. Each raised line portion 424 is configured as partof an arc about a different center, as illustrated in FIG. 4, for anexemplary embodiment.

According to a preferred embodiment of the invention, the line portion424 is formed with a pointed end 425 adjacent the downstream side,thereby to minimize deflection of backflow streams impinging thereon.

The resulting configuration provides a relatively enhanced length of theline portion, and thus of the filter barrier per unit area of the filterelement. It will be appreciated that the filter barrier defined by theraised line portion 424 defines a barrier between an upstream side ofthe filter, here typically the radially outward side of the lineportion, and the downstream side of the filter, typically the radiallyinward side of the line portion. Accordingly, it may be understood thatan increase in the length of the filter barrier per unit area of filterelement provides a corresponding increase in the filtering capacity ofthe unit per unit area of filter element, and per unit volume of afilter assembly made up of a stack of such filter elements. The raisedline portion 424 is formed with an array of grooves 423.

The spaces 426 between adjacent finger elements 422, which typically lieat the upstream side of the filter, define filtering volumes, whichaccomodate, according to a preferred embodiment of the invention, afilter cake.

At spaces 428, defined interiorly of each finger element 422, whichtypically lie at the downstream side of the filter, there are definedplanar dividers 429, which are recessed with respect to both the lineportions of the first and second surfaces, such that when a plurality offilter elements is arranged in registration in a stack, the planardividers define a multiplicity of backflow chambers 430 for enhanced andconcentrated backflowing. There backflow chambers are particularlysuitable for pressurized backflow cleaning by the backflow focussed jetproduced by the apparatus of FIGS. 1-3 described hereinabove.

It is a particular feature of the invention embodiment in FIG. 4 that onthe downstream side there are defined backflow chambers whichconcentrate the backflowing effect of a backflowing jet of pressurizedfluid, while at the same time, at the upstream side, particulate matterdislodged from the filtering barrier is free to fall out of engagementwith the filter stack.

Reference is now made to FIGS. 5-9B. The assembly shown in these figurescomprises a stack of identical filter elements 510 being of the typeillustrated in FIG. 4 and being formed of a plastic material, such aspolypropylene. The filter elements comprise identically patternedopposite first and second planar surfaces. Except for grooves 423, thetwo planar surfaces of each filter element are mirror images of oneanother, such that the line portions thereof on both first and secondsurfaces thereof are in registration, as are the spaces between fingersand inside fingers. The grooves 423 on the facing raised line portionsare preferably skewed with respect to one another.

Each planar surface of filter element 510 is formed with a filterbarrier defined by a raised line pattern 520, which preferably isarranged to extend continuously in generally undulating configuration,defining a plurality of finger elements 522. The raised line pattern 520typically defines the outline of each finger element 522 and may beconfigured to define a smooth outline or alternatively a notched orserrated pattern along the generally radially extending portion of eachfinger element 522.

As noted in connection with finger element 422 described hereinabove,the outline of each finger element is preferably curved along a portionof an arc. Each raised line portion is preferably configured as part ofan arc about a different center, as illustrated in FIG. 4.

The resulting configuration provides a relatively enhanced length of theline portion, and thus of the filter barrier per unit area of the filterelement. It will be appreciated that the filter barrier defined by theraised line portion 520 defines a barrier between an upstream side ofthe filter, here typically the radially outward side of the lineportion, and the downstream side of the filter, typically the radiallyinward side of the line portion. Accordingly, it may be understood thatan increase in the length of the filter barrier per unit area of filterelement provides a corresponding increase in the filtering capacity ofthe unit per unit area of filter element, and per unit volume of a stackof such filter elements.

It is a particular feature of the present invention that the upstreamside of the filtering barrier defined by raised line portion 520 is arelatively open volume, thus providing enhanced capacity for largeparticles during filtration and ease of particle disengagement duringregeneration and backflowing, while at the same time providing efficientfiltration of small particles.

In the embodiment of FIGS. 5-9B, the filter elements making up the stackof filter elements are maintained in precise azimuthal alignment, as bymeans of one or more azimuthal aligning protrusions 85 associated witheach stack of filter elements and registered by a rod (not shown)passing therethrough. Accordingly, when the first and second planarsurfaces are arranged in juxtaposed engagement, the finger elements 522on the facing first and second planar surfaces of adjacent filterelements are in precise registration, defining a filter barrier betweenthe upstream side of the filter and the downstream side. At thelocations where the finger elements on first and second surfaces meet intouching engagement, grooves 525 on either or preferably both planarsurfaces are engaged. Understanding of this engagement may be assistedby a consideration of FIG. 6, which is an enlargement taken along thelines VI--VI in FIG. 5.

It is a particular feature of the present invention that where groovesare formed on both facing line portions, such grooves 526 and 528 on theopposite engaging surfaces are mutually skewed, as illustrated in FIG.6, such that they define multiply intersecting paths for fluid flowtherethrough, there being defined at intervals along the pathway aparticle size gauge being the cross section of the single groove.

This configuration has a number of advantages, including the fact thatalong much of the pathway from the upstream side to the downstream sideacross the engaged first and second surfaces, the pathway is larger thanthe particle size gauge due to the effective combination of groovesformed on the opposite facing surfaces. The multiple interconnectionsbetween grooves provides multiple alternative paths for fluid, such thatfluid flow may continue notwithstanding blockage of certain passageways.The relatively long and intricate pathway of the fluid provides enhanceddepth of filtering, thus increasing filtering efficiency.

Reference is now made to FIG. 7, which corresponds to FIG. 6 but alsoshows the presence of filter cake and/or sediment during operation ofthe filter. The illustration shows an embodiment wherein the upstreamside is radially outward of the raised line portion 520 and thusintermediate finger elements 522 while the downstream side is at theradially inward side of the raised line portion 520 and thuscommunicates with the area and volume interior of each finger element522.

It is seen that fluid, such as water, carrying particulate matter,enters from the upstream side, as indicated by arrows 530, and depositsthe particulate matter 532 upstream of the raised line portion 520.

It may additionally be appreciated that a filter aid such asdiatomaceous earth, activated carbon or a filter cake may be employedand disposed at the upstream side of the stack of filter elements, asillustrated.

It is a particular feature of the present invention that the spacesbetween adjacent fingers 522 are open, such that when a plurality offilter disks 510 are stacked with the fingers 522 in registration,channels 560 are defined between adjacent fingers, as seen in FIGS.8-9B. These channels have particular importance when a filter aid, suchas a filter cake, is employed, as the filter cake may be located on theupstream surface of the filter disks 510 along the periphery of thefingers 522.

Assuming that the stack of filter disks 510 is arranged generallyvertically, it may be understood that when flow of fluid through thefilter from the upstream side to the downstream side is terminated, thefilter aid and accumulated filtered out particulate material, whichduring filtering is stuck onto the peripheral edges 524 of the fingers,as seen figuratively in FIG. 9A, tends to fall through the channels 560to the bottom of the filter housing, as seen figuratively in FIG. 9B.

Reference is now made to FIG. 10, which illustrates an alternativeembodiment of filter, which is identical to that illustrated in FIG. 1with the exception of the location of fluid inlet 78. It is noted thatin the embodiment of FIG. 1, the inlet 78 also functions as a backflowdrain and lies somewhat spaced from the bottom of the housing 72. InFIG. 10, the location of the inlet 78 in spaced relationship with thebottom of the housing 72 is emphasized. It will be appreciated bypersons skilled in the art that the arrangement of FIG. 10 may replacethat of FIG. 1 in all the embodiments of the invention illustrated inFIGS. 4-9B. FIG. 10 is also illustrative of a broader concept which isnot limited to disk filters or to filters having a backflow arrangement.

Upon termination of liquid flow through the filter assembly, the liquiddrains to the bottom of the housing, and the particulate matter,including filter aid material and solid particles separated from theliquid, falls into the liquid, the filter aid material falling to thebottom of the housing and the solid particles floating in or on theliquid, such that at least some of the filter aid material is retainedin the housing while the solid particles are flushed out the drain.

Upon resumption of pressurized liquid flow through the filter assembly,the filter aid becomes distributed on the upstream side of the filterassembly and carries out its normal function, having thus being cleaned,reoriented end recycled.

The drain may be separate from the inlet or identical therewith. In thelatter case, the filter apparatus preferably comprises a manuallyoperable multi-flow valve 125 having a normal position wherein liquid tobe filtered is coupled to the upstream side of the filter assembly and abackflow position wherein liquid to be filtered is prevented fromreaching the upstream side and wherein the drain communicating with theupstream side is coupled for draining to the atmosphere.

Reference is now made to FIG. 11, which illustrates an alternativeembodiment of filter, which is generally identical to that illustratedin FIG. 10 with the exception of the locations of rods 88. In theembodiment of FIG. 11, the rods 88, which tightly secure the filterdisks 82 together in stack 79, are disposed intermediate the inner andouter diameters of the stack. This arrangement of rods 88 eliminatesinterference with backflowing which would occur were the rods 88 locatedinwardly of the downstream surface of the stack 79 and also eliminatesthe waste of volume in the housing which would result were the rods 88to be located outwardly of the upstream surface, as shown in theembodiment of FIG. 10. Thus, the embodiment of FIG. 11 maximizes therelationship between stack diameter and inner diameter of the housing.

The embodiment of FIG. 11 is characterized in that it includes a stackof filter elements 79, or any other suitable filter assembly, which isconfigured to permit particulate matter to fall out of engagement withthe upstream side thereof to the bottom of the housing in the absence ofliquid flow through the filter assembly. It is appreciated that theforegoing is also true for the embodiments of FIG. 1-9B.

Reference is now made to FIG. 12, which illustrates a filter disk 600constructed and operative in accordance with a preferred embodiment ofthe present invention. Filter disk 600 is generally identical to thatillustrated in FIGS. 5-8 hereinabove, with the exceptions describedhereinbelow:

Filter disk 600 is formed with a plurality of finger elements 602 havinga non-radical configuration curved along a portion of an arc. Eachfinger may be seen to include a line portion 604, which correspondsgenerally to line portion 424, described above in connection with FIG.4. The line portion 604 for each finger may be considered to include anoutwardly facing portion 606 and an inwardly facing portion 608, joinedby an outward curved portion 610 and an inward curved portion 612.

According to a preferred embodiment of the present invention, theoutwardly facing portion 606 is longer than the inwardly facing portion608, such that application of a positive pressure gradient from theupstream side of the stack, here the outside thereof, to the downstreamside of the stack, here the inside thereof, as during normal filteringoperation, causes inward bending of the fingers 602 in a clockwise sensefor the configuration as illustrated in FIG. 12. Removal of the pressuregradient, as upon termination of the supply of pressurized fluid to befiltered, allows fingers 602 to snap back to their original positions.

Further in accordance with a preferred embodiment of the invention thereexists a very small difference in thickness of the filter elementbetween its radially inward portion and its extreme radially outwardportions, whereby the thickness of the radially outward portions is veryslightly less than that of the radially inward portion. This differencein thickness permits the finger elements 522 of adjacent filter elementsto be slightly spread apart in a direction parallel to axis 118 (FIG. 1)in response to the application of a backflow jet to the volume interiorof each finger element. This spreading apart assists in thedisengagement of particles accumulating from the stacked filter elementsbut is not sufficient to permit entry of small particles into the filterstack during normal filtering flow from the upstream side to thedownstream side.

Additionally in accordance with a preferred embodiment of the presentinvention, adjacent each of the inward curved portions 612 there isprovided a narrow, radially extending structural member 614, whichextends nearly but not completely to the inner edge of the disk 600.Structural members 614 provide necessary structural support for thedisks 600 while also functioning to define backflow chambers 616 betweenadjacent member 614. These backflow chambers 616 are relatively broadadjacent the downstream side of the stack for minimum interference witha jet of backflow fluid and then narrow as they extend betweenrespective outwardly facing and inwardly facing line portions 606 and608.

Additionally in accordance with a preferred embodiment of the presentinvention, and as noted above in connection with FIG. 11, accomodationis made for transversely extending rods 88, in the form of sockets 618which are located intermediate the inner and outer diameters of the disk600. According to a preferred embodiment of the invention, asillustrated in FIG. 12, the socket 618 is located in communication withthe upstream side of the disk 600 and is arranged as an enlargement ofinward curved portion 612, so as to minimize interference withbackflowing while minimizing the loss of filter surface area at thesocket.

Reference is now made to FIGS. 13A and 13B which illustrate the bendingand snap back action of the fingers 602 in accordance with the presentinvention. In FIG. 13A, the normal orientation of fingers 602, i.e. inthe absence of an applied pressure gradient, is illustrated in solidlines, while the bent position thereof, shown in exaggerated form forthe purpose of illustration only, is illustrated in broken lines. Infact the angular displacement of the outer ends of the fingers is quitesmall and is a function of the materials used for the filter elementsand of the operating pressure in the filter. In FIG. 13B, oppositebending upon backflowing is illustrated, with the normal orientation offingers 602 being shown in solid lines and the angular displacement ofthe outer ends of the fingers during backflowing being shown in brokenlines.

It is a particular feature of the present invention that the bending ofthe fingers, which occurs upon termination of normal filtering and alsotypically upon the onset of backflowing at a given region, serves toenhance disengagement of particles from the surface of the filter disks600.

Backflowing, which normally will not occur each time there is atermination of normal filtering, is typically accompanied by additionalbending in an opposite sense from the bending produced under normalfiltration operation, and thus produces enhanced disengagement of thefilter aid material from the stack.

It is also noted that upon backflowing, the fingers of adjacent disksare slightly separated from each other, thus enabling the space betweenthe grooves 526 and 528 to be locally and temporarily enlarged forenhanced backflowing.

FIG. 14 illustrates pictorially the disengagement of filter aid materialfrom a stack of filter disks when the fingers 602 snap back from theirbent positions (shown in broken lines) to their normal positions (shownin solid lines).

FIGS. 15A and 15B are enlarged sectional illustrations of thisphenomenon, showing the buildup of dirt and accumulation of filter aidmaterial prior to disengagement (FIG. 15A) and following disengagement(FIG. 15B).

It will be appreciated that the filter assembly may comprise anysuitable filtering element or assembly of elements although a stack offilter disks as described hereinabove is preferred. A backflowingarrangement as described hereinabove is useful in association with thefilter aid retaining arrangement described hereinabove but is notrequired.

Reference is now made to FIGS. 16-19, which illustrate an alternativeembodiment of the present invention wherein a central inlet and outletmanifold is provided. The embodiment of FIG. 16 is generally identicalto that shown in FIG. 11 with the following exception:

Disposed at the very bottom of the housing 72 is an inlet and outletmanifold 702 which is coupled to a fluid inlet/backflow drain conduit704 and to a filtered fluid outlet conduit 706. Fluid inlet/backflowdrain conduit 704 is typically connected to a three position valve suchas valve 125 shown in FIG. 11.

Fluid communication from a source of pressurized fluid via valve 125(not shown) to the upstream surface of the filter assembly isillustrated by arrows 708. Fluid communication from the upstream side ofthe filter assembly to the backflow outlet is illustrated by arrows 710.Fluid communication from the downstream side of the filter assembly tofiltered fluid outlet conduit 706 is illustrated by arrows 712.

According to one embodiment of the invention, the manifold is providedwith radially extending outlets, as shown in FIG. 18. According to analternative embodiment of the invention, the outlets may be arranged asillustrated in FIG. 19 to provide a tangent flow. In FIG. 19, thistangent flow of fluid to be filtered into the housing is illustrated byarrows 714.

Referring now to FIGS. 16-19, the structure of the manifold 702 will nowbe described. The manifold comprises a body member 721 which isconnected to conduit 704 and which defines an annular inlet passage 722,communicating with conduit 704. Body member 721 also defines a centraloutlet passage 724 which communicates with outlet conduit 706.

A collar member 728 threadably engages corresponding threading on thebody member 721 and is operative to secure the manifold in sealingengagement with an aperture 730 formed at the bottom of housing 72, bymeans of a sealing ring 732.

As seen in FIG. 17 and FIGS. 18 or 19, the collar member 728 comprises aplurality of upstanding members 734 which define shoulders 736 whichseat on the bottom of the housing 72 at the periphery of aperture 730.Defined between adjacent upstanding members 734 are inlet passages 738.

It is a particular feature of the manifold arrangement shown in FIGS.17-19 that both inlet and outlet to the filter are provided through asingle aperture in the housing 72.

It is a further particular feature of the present invention that should736 provides centering of the entire manifold assembly onto the housing72. It is noted that shoulder 736 comprises a surface 740 which lies ina plane parallel to axis 118 which provides the desired centering.

Shoulder 736 also comprises a surface 742 which lies in a planeperpendicular to axis 118 and which lies over the edge of housing 72adjacent to aperture 730, thereby pressing housing 72 against sealingring 732 for providing desired sealing upon tight threaded engagement ofthe collar member 728 onto the body member 721.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the invention is defined onlyby the claims which follow:

I claim:
 1. A filter comprisinga housing having an inlet and a draincommunicating with an upstream side and an outlet communicating with adownstream side, a filter element having a longitudinal inner volumedisposed within said housing generally along the axis of said housing,said longitudinal inner volume being in communication with thedownstream side and the exterior of said filter element being incommunication with the upstream side and; means for impingingpressurized fluid from at least one opening on said filter element fromthe longitudinal inner volume of said filter element for separatingparticles from said filter element, said means having at least oneopening on one end and arranged to be connected to a pressurized fluidsource on the other end, said means being disposed within saidlongitudinal inner volume and being arranged to move linearly along saidlongitudinal inner volume and rotate inside said longitudinal innervolume and being adapted for communication with an energy source forpowering said linear movement and rotational movements.
 2. A filteraccording to claim 1 where said means for impinging pressurized fluidincludes a rotatable head comprising at least one tangentially directedjet aperture so that a jet issuing therefrom will apply a force torotate said rotatable head within said filter element and will impingepressurized fluid on said filter element.
 3. A filter according to claim2 wherein said rotatable head includes at least one aperture providing adirected jet to impinge pressurized fluid on the filter element.
 4. Afilter according to claim 2 wherein said rotatable head includes atleast one tangentially directed jet aperture to provide a directedconcentrated jet to impinge pressurized fluid on the filter element. 5.A filter according to claim 2 wherein said means for impingingpressurized fluid including a positioning ring with ribs for desiredpositioning of said rotating head in an inner cylindrical downstreamvolume of said filter element whereby the axis of rotation of saidrotatable head is centered with respect to said inner cylindricaldownstream volume.
 6. A filter according to claim 1 wherein said meansfor impinging pressurized fluid is arranged for rotational movementwithin said longitudinal inner volume of said filter element by manualoperation.
 7. A filter according to claim 1 wherein said means forimpinging pressurized fluid is arranged for linear movement along saidlongitudinal inner volume of said filter element by manual operation. 8.A filter according to claim 1 wherein said means for impingingpressurized fluid is arranged for linear movement along the central axisof said filter element.
 9. A filter according to claim 1 wherein saidmeans for impinging pressurized fluid includes a positioning ring withribs corresponding to the curvature of an inner cylindrical downstreamsurface of the filter element for desired positioning of said means insaid inner cylindrical downstream surface.
 10. A filter according toclaim 1 wherein said means for impinging pressurized fluid includes apositioning ring with ribs corresponding to the curvature of an innercylindrical downstream surface of the filter element for desiredpositioning of said means during its linear and rotational movements.11. A filter apparatus comprisinga housing having an inlet and a drainin communication with an upstream side and an outlet in communicationwith a downstream side and; a stack of filter disks disposed within saidhousing for filtering fluid flowing from the upstream side to thedownstream side, said stack of filter disks having a longitudinal innercylindrical downstream surface being in communication with the outletand an outer upstream surface being in communication with the inlet anddrain; a jet nozzle assembly disposed mainly within a volume defined bysaid longitudinal inner cylindrical downstream surface, said jet nozzlecomprising on one end at least one jet output aperture for impingingpressurized fluid on said filter element, the other end arranged to beconnected to a source of pressurized fluid, said jet nozzle assemblybeing arranged to move inside said volume, said longitudinal innercylindrical downstream surface being arranged to support said jet nozzleassembly and to guide its movement within said volume.
 12. A filterelement according to claim 11 including a guiding support on the innercylindrical downstream surface of said filter element for guiding saidjet nozzle assembly in its linear movement.
 13. A filter elementaccording to claim 11 , wherein said jet nozzle assembly is arranged tobe guided in its linear movement within said inner cylindricaldownstream surface from said guiding support.
 14. A filter apparatuscomprisinga housing have a central aperture, a filter barrier disposedwithin said housing for separating predetermined particles from a fluidflowing from an upstream side to a downstream side of said filterbarrier, an external manifold connected to the housing and to saidcentral aperture and defining first and second volumes comprising aninlet, a drain and an outlet, wherein said first volume is incommunication with said inlet and drain and the upstream side throughsaid central aperture and said second volume is in communication withsaid outlet and the downstream side through said central aperture suchthat during filtration operation non-filtered fluid entering from saidinlet to said first volume passes through said central aperture to theupstream side and filtered fluid flowing from the downstream sidethrough said central aperture to said second volume to said outlet,wherein said filter barrier includes a filter element having alongitudinal inner volume disposed within said housing generally alongthe axis of said housing, said longitudinal inner volume being incommunication with the downstream side and the exterior of said filterelement being in communication with the upstream side, and means forimpinging said filter element with pressurized fluid from at least oneopening for separating particles from said filter element, said at leastone opening being located on one end of said means, said means beingarranged to be connected to a pressurized fluid source on the other end,said means being disposed within said longitudinal inner volume andbeing arranged to move linearly along said longitudinal inner volume androtate inside said longitudinal inner volume and being adapted forcommunication with an energy source for powering said linear rotationalmovements.
 15. A filter according to claim 14 wherein the filter elementis a stack of filter disks.
 16. A filter according to claim 15 whereinat least some of the filter element disks are of a finger configuration.17. A filter according to claim 14 wherein said central aperture islocated in the bottom of said housing.
 18. A filter according to claim14 wherein said external manifold includes a threaded device disposedwithin said housing for connecting said external manifold to saidhousing through said central aperture.
 19. A filter according to claim14 wherein said central aperture is threaded circumferentially.
 20. Afilter according to claim 19 wherein said external manifold is threadedand threadedly connected to said central aperture.
 21. A filteraccording to claim 14 wherein said external manifold comprises an inletaperture, an outlet aperture and a drain aperture.
 22. A filteraccording to claim 14 wherein said external manifold comprises one inletand drain aperture and an outlet aperture.
 23. A filter according toclaim 14 including a distributor disposed between the inlet and theupstream side for distributing the flow of non-filtered fluid enteringto the upstream.
 24. A filter according to claim 14 wherein said centralaperture is located on the upper side of said housing.
 25. A filteraccording to claim 14 wherein said external manifold includes a threadeddevice disposed within said housing for connecting said externalmanifold to said housing through said central aperture.